[cert] capitalize python class constants (#5080)

According to PEP8, constants should be written in all capital letters.

This commit capitalizes these constants:
- thread_cert.TestCase.topology
- thread_cert.TestCase.support_ncp

tests/scripts/thread-cert/test_service.py

@@ -49,9 +49,9 @@ SRV_1_SERVER_DATA = 'qux'
 
 
 class Test_Service(thread_cert.TestCase):
-    support_ncp = False
+    SUPPORT_NCP = False
 
-    topology = {
+    TOPOLOGY = {
         LEADER: {
             'channel': 12,
             'mode': 'rsdn',